The present disclosure relates generally to information handling systems, and more particularly to optimizing the equalization of pulse amplitude modulated signals transmitted by information handling systems.
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems such as, for example, server devices, switch devices, and/or other computing devices known in the art, use modulation techniques to transmit information in signals sent to other computing devices. For example, Non-Return-to-Zero (NRZ) is a modulation technique in which information is provided in a signal via binary code in which ones are represented by a first condition (e.g., typically a positive voltage) and zeros are represented by a second condition (e.g., typically a negative voltage.) However, as higher signal transmission speeds become more desirable, NRZ become bandwidth inefficient. In order to address these issues, Pulse Amplitude Modulation (PAM) techniques such as, for example, PAM with a 4-level modulation scheme (PAM4), may be implemented to achieve high data rates using less bandwidth than NRZ.
However, channel losses (e.g., losses due to the printed circuit board, silicon package, connectors, vias, and/or other elements that are part of the signal transmission subsystem in the computing device) can negatively affect signals transmitted using PAM4 (e.g., making it difficult to distinguish between the bits being transmitted at different signals levels), and equalization of those signals is often implemented in order improve signal integrity (e.g., which ensures that bits transmitted at different signals levels may be identified at those signal levels and/or distinguished from each other.) However, signals transmitted using PAM4 produce a complicated eye diagram (e.g., including three slices and 12 distinct transitions between levels), and the equalizations and other signal optimizations for signals transmitted using PAM4 that have been adapted from binary signal equalization methods may require a variety of approaches to produce signals with desired characteristics. For example, conventional PAM4 equalization systems may equalize signals transmitted using PAM4 and based either on bit information (“per-bit equalization”) or based on symbol changes (“per-symbol equalization”). However, the channel losses discussed above can change based on changes to the signal transmission subsystem in the computing device, and thus the use of either per-bit equalization or per-symbol equalization can result in non-optimal equalization of signals transmitted using PAM4 in many instances. For example, when a signal over-equalized, the signal may experience “overshooting” as the levels start mixing with each other.
Accordingly, it would be desirable to provide an improved pulse amplitude modulation equalization system.